* Factor out ASTContext plugin loading to newly introduced 'PluginLoader'
* Insert 'DependencyTracker' to 'PluginLoader'
* Add dependencies right before loading the plugins
rdar://104938481
Driver uses its path to derive the plugin paths (i.e.
'lib/swift/host/plugins' et al.) Previously it was a constant string
'swiftc' that caused SourceKit failed to find dylib plugins in the
toolchain. Since 'SwiftLangSupport' knows the swift-frontend path,
use it, but replacing the filename with 'swiftc', to derive the plugin
paths.
rdar://107849796
Make a single 'PluginRegistry' and share it between SwiftASTManager,
IDEInspectionInstance, and CompileInstance. And inject the plugin
registry to ASTContext right after 'CompilerInstance.setup()'
That way, all sema-capable ASTContext in SourceKit share a single
PluginRegistry.
Macro expansion buffers, along with other generated source buffers,
need more precise "original source ranges" that can be had with the
token-based `SourceRange`. Switch over to `CharSourceRange` and provide
more thoughtfully-determined original source ranges.
Each macro expansion buffer was getting parsed twice: once by
ParseSourceFileRequest (which is used by unqualified name lookup) and
once to parse the expression when type-checking the expanded macro.
This meant that the same code had two ASTs. Hilarity ensures.
Stop directly invoking the parser on macro-expanded code. Instead, go
through ParseSourceFileRequest *as is always the right way*, and dig
out the expression we want.
Establish the relationship for generated sources, whether for macro
expansions or (via a small stretch) replacing function bodies with
other bodies, in the source manager itself. This makes the information
available for diagnostic rendering, and unifies a little bit of the
representation, although it isn't used for much yet.
Introduce a new source file kind to describe source files for macro
expansions, and include the macro expression that they expand. This
establishes a "parent" relationship
Also track every kind of auxiliary source file---whether for macro
expansions or other reasons---that is introduced into a module, adding
an operation that allows us to find the source file that contains a
given source location.
These libraries formed a strongly connected component in the CMake build graph. The weakest link I could find was from IDE to FrontendTool and Frontend, which was necessitated by the `CompileInstance` class (https://github.com/apple/swift/pull/40645). I moved a few files out of IDE into a new IDETools library to break the cycle.
